General information on current transformers
Current transformers are predominantly utilised in areas in which it is not possible to measure current directly. They are a special type of transformer with a defined degree of precision (class), which translates the primary current into a (usually) smaller, standardised secondary current, as well as galvanically separating primary and secondary circuits from each other. The physical saturation (especially with monitoring CTs) of the core material additionally guarantees protection of the secondary circuit from higher currents.
It is fundamentally possible to distinguish between single-phase current transformers and winding current transformers. The most frequent form of single-phase current transformer is the moulded case feed through current transformer, which is plugged onto the current-carrying phase and therefore forms a transformer with primary winding (and secondary windings in accordance with the transformation ratio).